The invention relates to an injection device, in particular for an exhaust-gas aftertreatment system of an internal combustion engine.
Injection devices of the aforementioned type are known. German laid-open specification DE 10 2006 912855 A1 discloses, for example, an injection system comprising a nozzle module which is assigned to an exhaust-gas pipe of an internal combustion engine in order to inject pressurized liquid exhaust-gas aftertreatment agent there into the exhaust gas. In the case of motor vehicles having an internal combustion engine, exhaust-gas legislation requires, inter alia, that the pollutant NOx must be reduced. A method which is frequently used here is the so-called SCR process (SCR=selective catalytic reduction) in which the pollutant NOx is reduced to nitrogen and water with the aid of a liquid exhaust-gas aftertreatment agent, which is generally an aqueous urea solution. The exhaust-gas aftertreatment agent is sucked in through an injection device from a tank and then injected into the exhaust gas. A corresponding injection device is also known from EP 1 878 920 B1, for example. In that document, the injection device has a valve piston which at first compresses exhaust-gas aftertreatment agent by means of an electromagnetic actuator and then injects it into the exhaust gas. The valve piston is then moved back into its starting position by a spring element, with the result that fresh reducing agent is sucked in. To achieve a high NOx reduction, it is necessary for the exhaust-gas aftertreatment agent to be mixed particularly effectively with the exhaust gas. For this purpose, it is advantageous if the injected spray is very fine or contains small drops. In the case of the cited publications, injection devices are provided which have an inner-opening injection valve. An inner-opening injection valve is to be understood as meaning a valve in which a valve tip of the valve piston interacts—as viewed in the throughflow direction of the throughflow opening—with a valve seat provided upstream of a throughflow opening.
German laid-open specification WO 94/00686 also discloses a perforated injection disk for injection valves which is provided with a plurality of injection openings for the targeted establishment of a spray.